Re: [ATM] Compensating sag of the truss frame by flexibility in themirror cell

["Robert Houdart" <robert.houdart@cruxis.be>]

Roy,

> Don't forget that the Serrurier truss is based on parallelogram action
at 
> both ends, so the optics stay in alignment as both ends of the
structure
> sag 
> by an equal amount.  Looks like your idea is based on a slight tilt of
the 
> primary to compensate top-end flexure -- But tilt of the optics can
cause 
> decollimation.  If the truss supporting the secondary sags, and the
>  primary 
> is also tilted, how can the telescope still be in perfect collimation?
Or 
> have I missed something?

Correct, it's not exactly like a Serrurier.

Note that the mirror tilt is tiny (only 1:15,0000 or 14 arc seconds).
It's difficult to put an eyepiece in a focuser with an accuracy coming
even close to this.

What is interesting in the concept is the awareness that two otherwise
negligible effects exist and can be used to compensate each other,
leaving only an extremely small mirror tilt as collimation error.

Robert

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